"... the Apostle Peter declared that the Church was built by the Holy Spirit. For you read that he said: 'God, Who knows the hearts of men, bore witness, giving them the Holy Spirit, even as was given to us; and He made no distinction between us and them, purifying their hearts by faith' (Acts 15:8-9). In which is to be considered, that as Christ is the Cornerstone, Who joined together both peoples into one, so, too, the Holy Spirit made no distinction between the hearts of each people, but united them."

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Perfection... is clearly not achieved simply by being naked, by the lack of wealth or by the rejection of honors, unless there is also that love whose ingredients the apostle described (cf. I Cor. 13) and which is to be found solely in purity of heart. Not to be jealous, not to be puffed up, not to act heedlessly, not to seek what does not belong to one, not to rejoice over some injustice, not to plan evil - what is this and its like if not the continuous offering to God of the heart that is perfect and truly pure, a heart kept free of all disturbance?

— John Cassian